Manchester United youngster Joel Pereira made his debut against Wigan... Why was Jose Mourinho so keen to give him a game?

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Usually a Manchester United goalkeeper is only replaced if he is injured or 'having a Massimo Taibi', so Sergio Romero must have been perplexed when he saw his number go up.

Joel Pereira, a name probably not familiar to many, came on his place. Romero was not injured and United had not conceded a goal. It was one of those changes that raised eyebrows but as it had no impact on the course of the game was hardly quibbled.

Post-match Jose Mourinho offered such a simple explanation for the change as if it were an weekly occurrence. He said: '[Axel] Tuanzebe and Joel [Pereira], for them it was the first match and it's always a nice moment, for every player, it's always a moment that stays with them.'

Joel Pereira made his Manchester United debut as a substitute against Wigan in the FA Cup

The 20-year-old keeper came on in place of Sergio Romero with just over 10 minutes to go

Post-match Jose Mourinho spoke of giving the youngster a 'nice moment' at Old Trafford

With 10 minutes left and the tie won there was no harm in the making the change. For a 20-year-old goalkeeper whose previous first team experience has come at Rochdale and Belenenses it was undoubtedly a nice moment to play at Old Trafford.

Without reading too much into a brief substitute appearance in a cup tie against lower-league opposition, his introduction perhaps speaks to Mourinho's faith in the young keeper.

The Swiss-born Portuguese youth international was recalled from his latest loan stint with Belenenses to act No 3 after the United boss sanctioned Sam Johnstone's own loan to Aston Villa.

The Old Trafford chief said at the time: 'We have a young goalkeeper in Joel [Pereira], a goalkeeper that played many minutes in the past six months in the Portuguese Premier League and now it's time for Sam [Johnstone] to play six months.'

Sam Johnstone was allowed to go on loan after Pereira was recalled from Belenenses

Pereira is clearly trusted and why not? He has been with the club's academy since moving to Manchester four years ago from Swiss second-tier side Neuchatel Xamax. 

After playing in the United age group sides the then 19-year-old got his first senior opportunity in a month-long loan spell at Rochdale in October 2015.

On debut Pereira was named man of the match and saved a penalty but could not prevent a 1-0 Johnstone's Paint Trophy defeat to Morecambe. Still, Dale boss Keith Hill was impressed enough to tip his young stopper to be a 'top, top goalkeeper' and described him as an 'exceptional talent'.

Signed from from Swiss side Neuchatel Xamax, Pereira gained experience at Rochdale

Mourinho clearly appreciates the work done by the staff at Carrington and declined to take take credit for Pereira's progression after the Wigan win.

'[It's] not my work, the work was made in the academy where the players were since they were really young kids,' said Mourinho.

'Also Joel was in Portugal where he played six months, so not my work at all, I was the guy who gave them the opportunity.'

In a recent interview with the United website Pereira spoke of his 'love' for Mourinho. But perhaps the most interesting takeaway from the piece was the youngster's confidence and desire to lean.

David de Gea will not be replaced any time soon but Pereira considers himself in the first-team

He said: 'It's good to be considered a first-team player now and I'm training every day with the first team and in the changing room with them. I think it's very good for me and my development too. 

'I get to work with world-class players as well. We have amazing strikers who are very good finishers so, of course, it is very good for me and I learn a lot every day.' 

Buying into Mourinho's methods is key to success under the manager not known to trusting youth. Whilst it is clear Pereira has a long way to go before thinking about replacing David de Gea, the man he replaced on Sunday might be starting to feel less secure.